This invention relates to a semiconductor memory device comprising a set of cross-coupled inverters having a pair of inverters.
In general, a static random access memory (SRAM) is known as a semiconductor device comprising a plurality of memory cells each of which will be called a static memory cell. Each of the static memory cells is composed of a set of cross-coupled inverters having a pair of inverters. Each of the inverters comprises one transistor and one load element. More particularly, a P-channel transistor or a resistor is used as the load element.
In general, the P-channel transistor load memory cell is more stable against noise or alpha rays than the resistor load memory cell. However, the P-channel transistor load cell still has unstability based on the noise or the alpha rays. In order to prevent this unstability, a conventional SRAM is disclosed in proceedings C-427 published on Autumnal Conference of the Institute of Electronics, Information, and Communication Engineers in 1991. The conventional SRAM comprises a plurality of static memory cells each of which has a set of cross-coupled inverters and a delay circuit having a high resistance value. In the conventional SRAM, it is possible to prevent the unstability of the static memory cell that is based on the noise or the alpha rays as will later be described in detail.
However, the resistance value of the delay circuit decreases in the static memory cell of the conventional SRAM as the static memory cell of the conventional SRAM is micronized in size. When the resistance value of the delay circuit decreases, it is difficult to obtain a delay effect of the delay circuit as will later be described. As a result, it is difficult to prevent the conventional SRAM from the unstability based on the noise or the alpha rays when the static memory cell of the conventional SRAM is micronized in size.